The present invention relates to a seat belt retractor.
A seat belt retractor according to the invention has an electric motor. Such a seat belt retractor is known from EP 0893313 A2. The present invention provides a force-absorbing bearing with direct rotary connections, for example by coupling the planet carrier to the belt reel, so that forces emanating from the belt reel in a crash do not influence operation of the electric motor, in particular in the region of the gap between the stator and rotor poles.
In a seat belt retractor of this type an electric motor which can be constructed as a flat motor as is known for example from DE 43 32 205 A1 is provided on one side of the frame. In known seat belt retractors torques supplied by the electric motor are caused to act on the winding shaft via a gear mechanism. The known flat motor has a planet gear coaxially arranged in the stator, the planet carrier of which forms the output of the flat motor.
In the present invention the planet carrier is mounted externally in a cylindrical external bearing which is formed on an adapter flange connected non-rotatably to one leg of the frame. Internally the planet carrier is mounted on a bearing journal projecting axially from the belt reel. This bearing journal can optionally be connected integrally to a torsion bar that extends axially into the interior of the belt reel and forms a load limiter. The coupling of the electric motor and the planet carrier to the belt reel, forces which are effective between the electric motor and planet carrier and the belt reel, in particular in the case of a crash, are absorbed by the support formed by the frame leg and the adapter flange. The adapter flange and frame leg are preferably connected with an interlocking fit to form a rigid support. Forces emanating from the belt reel, in particular during the forward displacement of the vehicle occupant after blocking of the belt reel, are absorbed by these supports without affecting the region of the air gap between the stator and rotor poles.
The rotor of the electric motor can be rotatably mounted on a housing secured to the adapter flange, in particular by means of a cylindrical external bearing provided on the housing. In addition a cylindrical internal bearing can be formed on the rotor by the bearing journals projecting from the belt reel.
A coupling operating between the planet carrier and the belt reel can be arranged between an end face of the belt reel and a side face of the adapter flange, in particular in the plane of the lateral frame leg. An interlocking covering of the coupling toward the outside can therefore be achieved by the adapter flange.
The adapter flange can be adapted to respective lateral frame legs of conventional seat belt retractors so that a connection which is non-twisting is achieved between seat belt retractor frame and adapter flange. The adapter flange can also be constructed symmetrically for this purpose. In order to improve the twisting safeguard, flange strips that surround the external contour of the respective lateral frame leg in an interlocking manner can be provided on the adapter flange. As a result of this a position-specific assembly of the adapter flange on the lateral frame leg is furthermore achieved.